This invention relates to a method of processing a silver halide photographic element. It particularly relates to the rapid processing of a photographic element in a single processing chamber.
Conventional processing of photographic material requires the use of large tanks of processing solutions. Each tank contains a processing solution such as developer, bleach, fixing solution, or washing solution. The material is transported through each tank in turn, typically in a sinusoidal manner. There is a tendency for the solutions to carry over from one tank to another leading to pollution of the solutions. Conventional processing has several other drawbacks. The temperatures which can be utilized are limited and, therefore, the process is slow. The composition of the solutions must be stable over long time periods in the processing tanks. Replenishment of the solutions is difficult to control. The processing apparatus is also very large due to the number of processing tanks.
In color negative film processing carried out in small continuous processors or xe2x80x9cminilabsxe2x80x9d the film passes through each stage of the process and from one tank of processing solution to the next tank of processing solution in a sinusoidal manner. The processing tanks used in a xe2x80x9cminilabxe2x80x9d processor are usually within the range of 3 to 20 litres volume for each tank depending on the individual design. In Process C-41SM the developer stage has one tank, the bleach stage has one tank, the fixer stage consists of two tanks, and the stabilizer stage consists of three tanks. This gives the total number of tanks as seven. It can be seen that each processing solution is in at least one separate tank, and the film passes sequentially through these tanks. The amounts of processing solution used in a minilab vary with the type of solution and processor, but a developer replenishment rate is generally about 375-500 mL/m2, a bleach replenishment rate is about 130 mL/m2, a fixer replenishment rate is about 200-900 mL/m2, and a rinse or stabilizer replenishment rate is about 775-1000 mL/m2.
A method of processing photographic material in a single processing chamber is described in U.S. application Ser. No. 09/920,495 of Twist et al filed Aug. 1, 2001. One of the advantages of the process is that small volumes of processing solutions are used per unit surface area of the photographic material that is processed (9.4 to 1900 mL/m2). Examples of the process include the sequential application and removal of developer+stop, bleach, fixer, and rinse solutions from the processing chamber. A rapid process example applies developer solution at 280 mL/m2 and stop, bleach, and fixer solutions each at 375 ml/m2.
A compact processing method that comprises the sequential addition to a processing chamber of a first processing solution (for example, a developer, fixer, or bleach solution) to process the material and then a second processing solution (for example, a stop, fixer, bleach, or bleach-fixer solution) to process the material further without removing the first processing solution has been disclosed in U.S. application Ser. No. 10/012673 of Twist filed Oct. 30, 2001. Such a process is referred to hereafter as a merged process. In a preferred version of the method a developer solution is first added to the chamber to develop the material. Then, a fixer solution is added to the developer solution within the chamber for the purpose of stopping development and initiating fixing. Subsequent to this, a bleaching agent solution is added to the developer/fixer mixture within the chamber to bleach developed silver and complete the fixing of the material. Again, low volumes of processing solutions are applied. For color negative film processing, the first processing solution of the method is applied at 50 to 2850 mL/m2, and the second and subsequent processing solutions are applied at 6 to 2000 mL/m2. Highly concentrated processing solutions can be used.
Useful concentrations of fixing agents and bleaching agents in rapid versions of such a merged processing method for color negative films have been disclosed, for example, in U.S. application Ser. No.10/012,673 of Twist filed Oct. 30, 2001 and U.S. application Ser. No. 10/051,074 of Hall et al filed Jan. 30, 2002. Fixing agent concentrations (thiosulfate is preferred, and ammonium thiosulfate is more preferred as a fixing agent for rapid fixing) above 0.5 mol/L are useful in processing solution mixtures of the method. The fixing agents should be preferably at a total concentration from about 0.75 mol/L to about 2.0 mol/L in processing solution mixtures of the method in order to process rapidly without costly, wasteful use of fixer. The preferred Fe(III)chelate bleaching agents should be at a total concentration from about 0.09 equivalents/L to about 0.6 equivalents/L in the processing solution mixtures of the method in order to process rapidly without costly, wasteful use of bleaching agent. A more preferred Fe(III)chelate bleaching agent concentration is from about 0.12 equivalents/L to about 0.6 equivalents/L. This concentration of Fe(III)chelate bleaching agent is that concentration resulting after the oxidation of any developing agent in the mixture has taken place. Such oxidation results in the reduction of an equivalent of Fe(III)chelate to Fe(II)chelate for each equivalent of developing agent that is oxidized and results in a lower concentration of Fe(III)chelate bleaching agent in the mixture that is available for bleaching silver. The more preferred Fe(III)chelate bleaching agents are Fe(III) complexes of ethylenediaminetetraacetic acid, 1,3-propanediamine-N,N,Nxe2x80x2,Nxe2x80x2-tetraacetic acid, ethylenediamine-N-(2-carboxyphenyl)-N,Nxe2x80x2,Nxe2x80x2-triacetic acid, ethylenediaminedisuccinic acid (particularly the S,S-isomer), ethylenediaminemonosuccinic acid, N-(2-carboxyethyl)aspartic acid, and N-methyliminodiacetic acid, which may be used alone or in combination.
When processing solutions are added to the processing chamber to form a bleach-fixing solution mixture, the pH of the bleach-fixing solution mixture should be from about 4 to about 8, preferably from about 4.5 to 7, and more preferably from about 4.5 to 6.5. At pH""s lower than about 4.5, bleaching occurs quite rapidly, but the formation of colorless (leuco) forms of cyan image dyes may occur which degrades image quality. At pH""s higher than about 6.5, bleaching takes place more slowly. Also, the non-imagewise formation of image dye from bleach-induced dye formation (bleach stain) can occur at higher bleach-fixer pH""s, causing.densities of the photographic material to be unacceptably high.
These desired concentrations of fixing agents and bleaching agents can be achieved with low applied volumes of stop, fixer, bleach, or bleach-fixer solutions added to the developer solution when the volume of applied developer solution is also kept low. This is because the volume of each solutionxe2x80x94developer, stop, fixer, bleach, or bleach-fixerxe2x80x94dilutes the constituents of each solution comprising the merged mixture. In addition, the developing agent reduces some of the bleaching agent in the mixture making less available to accomplish bleaching of developed silver. Lower volumes of solutions can be used to achieve the necessary processing concentrations if they are more concentrated in fixing and bleaching agents, but even so, there is a limit to the solubility of processing agents in aqueous solution. The pH parameters can also be easily met when the volume of applied developer solution is kept low. This is because with less applied developer solution, there is less alkalinity present that must be neutralized to stop development and to adjust the pH into the range for rapid and effective desilvering by the merged mixture. This alkalinity is neutralized by providing the stop, fixer, bleach, or bleach-fixer solutions with a suitably low pH and a quantity of one or more acid-providing buffers. Applied processing solutions are measured in terms of the volume added per unit area of material to be processed, for example, in milliliters of solution per square meter of photographic material.
For example, in the merged process method the applied volume of various processing solutions can be as shown below.
Often, however, a larger volume of developer is desirable or necessary in order to develop the material more rapidly or with improved uniformity. However, if a larger volume of developer is applied, then a larger volume of fixer (or a more concentrated fixer solution), a larger volume of bleach solution (or a more concentrated solution of bleaching agent), or a larger volume of a bleach-fixer solution (or a more concentrated bleach-fixer solution) must be applied to achieve the desired concentrations of fixing and bleaching agent in the resulting mixture in order to process sufficiently rapidly. Larger amounts of acid-providing buffers must be used to neutralize the alkalinity of the developer solution. The larger volumes of processing solution, or the use of more concentrated processing solutions, increase the cost of running the process. In particular, larger volumes of bleach or bleach-fixer solutions or more concentrated bleach or bleach-fixer solutions contribute significantly to the cost of the processing chemistry for the process.
A method of processing is needed which reduces the amount of bleaching agent, provided by a bleach solution or bleach/fix solution, which must be utilized in a merged process utilizing a single chamber processor. This is particularly needed when larger volumes of developer solution are required.
A method for processing a silver halide color photographic material comprising the steps of loading the material into a chamber adapted to hold the material therein; introducing a measured amount of a developer solution into the chamber; developing the photographic material with the developer solution; introducing into the chamber a measured amount of a processing solution which arrests development, without removing th e developer solution, to form a developer/stop solution mixture; processing the photographic material with the developer/stop solution mixture, substantially removing all of the developer/stop mixture solution from the chamber; then providing in the chamber a bleach/fixer solution mixture comprising a bleaching agent and a fixing agent; and processing the photographic material with the bleach/fixer solution mixture; wherein the color developer solution is utilized in the amount of greater than or equal to 375 ml/m2 of the photographic material that is processed; and wherein the total volume of solution or solution mixture for each processing stage is spread over the whole area of the photographic material in a repetitive manner to enable uniform processing. In one embodiment the ratio of the bleaching agent equivalents utilized in the process to the volume of color developer solution utilized in the process, in liters, is less than or equal to 0.48.
This invention provides a more cost effective method for processing silver halide elements in a single chamber processor by reducing the amount of bleaching agent, provided by a bleach solution or bleach/fix solution, which must be utilized. The inventive process also uses less total processing solution volume. The advantages of the invention become greater if the applied developer volume must be increased further in order to process satisfactorily, such as with greater rapidity or uniformity.